This invention relates to color printing, and more particularly, to color laser printing systems. Such structures of this type, generally, employ a rotatable, carousel type shuttle color printer with all in one electrophotographic (EP) cartridges.
It is known, shuttle type color printers to employ a paper drive. Exemplary of such prior art is commonly assigned U.S. Pat. No. 5,978,642 (""642) to D. J. Arcaro-et.al., entitled xe2x80x9cColor Printer with Shuttle Type Paper Drive and Method.xe2x80x9d While the ""642 reference utilizes a shuttle type paper drive, the disengaging of the transfer roller from the photoconductor drum during paper reversal does not yield much more than 1 mm clearance between the paper and the photoconductor drum. This 1 mm clearance may result in an inadvertent pickup of toner by the paper, which will adversely affect the quality of the printing on the paper. Therefore, while this 1 mm clearance is sufficient in many instances, it is desirable to increase clearance to 5 mm for a truly robust solution.
It is also known, in color image forming apparatus, to employ rotatable image forming units. Exemplary of such prior art is U.S. Pat. No. 5,809,380 (""380) to N. Katakabe et. al., entitled xe2x80x9cColor Image Forming Apparatus with Plural Color Units.xe2x80x9d While the ""380 reference utilizes rotatable image forming units, these units create an intermediate image before it is transferred to paper. Consequently, a more advantageous color printer would be presented if the use of the intermediate image could be eliminated.
It is apparent from the above that there exists a need in the art for a carousel type shuttle color printer with all in one EP cartridges, which at least equals the printing characteristics of the known color printers, but which at the same time provides an increased gap between the photoconductor drum and the transfer roller while the paper is being shuttled. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.
Generally speaking, this invention fulfills these needs by providing a carousel type shuttle color printer, comprising a rotatable color image forming unit having a plurality of different color development stations, wherein the color image forming unit is located substantially on one side of a paper to be printed upon such that the image forming unit substantially contacts the paper, and a paper transfer means located substantially adjacent to the other side of the paper such that the paper transfer means substantially contacts the paper, wherein the image forming unit rotates to an intermediate, non-printing position during a switching between the plurality of different color development stations to produce a gap between the color image forming unit and the paper transfer means.
In certain preferred embodiments, the gap is approximately 5 mm. Also, the carousel type shuttle color printer can print in a simplex or duplex mode. Finally, the paper transfer means consists of a paper shuttle path, pinch rollers, a transfer roller, and a transfer belt.
In another further preferred embodiment, the rotation of the color image forming unit creates the gap between the photoconductor drum and the transfer roller such that the paper can be easily shuttled past the color image forming unit without adversely affecting the quality of printing on the paper.
The preferred color printer, according to this invention, offers the following advantages: excellent printing characteristics; ease of assembly and repair; good stability; excellent durability; and good economy. In fact, in many of the preferred embodiments, these factors of printing characteristics, durability, and economy are optimized to an extent that is considerably higher than heretofore achieved in prior, known color printers.
The above and other features of the present invention, which become more apparent as the description proceeds, are best understood by considering the following detailed description in conjunction with the accompanying drawings, wherein like characters represent like parts throughout the views: